Catechins are known to have a suppressing effect on increase in cholesterol level and an inhibitory effect on α-amylase activity (Patent Documents 1 to 2). To develop such physiological effects of catechins, it is necessary for an adult to drink 4 to 5 cups of tea per day. Accordingly, there is a desire for technology that permits addition of catechins at a high concentration to beverages to facilitate ingestion of a large amount of catechins. As one of the methods, catechins are added in a dissolved form to a beverage by using a concentrate of green tea extract (Patent Document 3) or the like.
As processes for extracting catechins with a stable taste from green tea or semi-fermented or fermented tea leaves, there are known a two-step extraction process in which extraction is conducted with slightly warm water, and subsequent to heating, extraction is conducted again and an extraction process under strongly acidic conditions (Patent Documents 4-6). However, these extraction processes are limited to the extraction of catechins from tea leaves, and are intended to achieve only stabilization of a taste of a purified product and maintenance of a good taste.
Further, catechins are generally known to be sparingly soluble in organic solvents. It is also known that the extraction of catechins can be promoted in a weakly acidic range. A high proportion of an organic solvent, however, involves such a problem that the efficiency of extraction of catechins is substantially lowered (Patent Document 7).
In tea leaves, however, caffeine component is also contained generally at from 2 to 4 wt % although catechins are contained in an amount as much as about 15 wt %. As caffeine exhibits a central stimulant effect, it is used for the suppression of sleepiness. On the other hand, its excessive ingestion is considered to bring about adverse effects such as nervosity, nausea and hyposomnia. Investigations have, therefore, been made for processes that selectively remove only caffeine from caffeine-containing compositions.
Proposed is, for example, a process in which caffeine is selectively removed by bringing a caffeine-containing, aqueous solution into contact with activated clay or acid clay (Patent Document 8). However, this process is accompanied by such a problem that the color may be deteriorated in some instances, although caffeine can be selectively removed by simply using activated clay or acid clay.    [Patent Document 1] JP-A-60-156614    [Patent Document 2] JP-A-03-133928    [Patent Document 3] JP-A-59-219384    [Patent Document 4] JP-A-2003-219799    [Patent Document 5] JP-A-2003-219800    [Patent Document 6] JP-A-2003-225053    [Patent Document 7] JP-A-2004-147508    [Patent Document 8] JP-A-06-142405
The present invention provides a packaged beverage containing from 0.03 to 1.0 wt % of non-polymer catechins, wherein the packaged beverage contains a low-caffeine green tea extract obtained by a method of bringing a green tea extract into contact with a 91/9 to 97/3 by weight mixture of an organic solvent and water (i.e. a mixture of an organic solvent and water at a weight ratio of 91/9 to 97/3), activated carbon, and acid clay or activated clay.
The present invention also provides a process for producing a low-caffeine green tea extract containing from 25 to 90 wt % of non-polymer catechins based on a dry weight of the extract, which comprises bringing a green tea extract into contact with a 91/9 to 97/3 by weight mixture of an organic solvent and water, activated carbon, and acid clay or activated clay.
The present invention further provides a low-caffeine green tea extract, wherein the low-caffeine green tea extract contains from 40 to 90 wt % of non-polymer catechins based on a solid content of the low-caffeine green tea extract, and a weight ratio of the non-polymer catechins to caffeine is from 25 to 200.
The present invention still further provides a process for selectively removing caffeine from a caffeine-containing catechin composition, which comprises dispersing a green tea extract in a 91/9 to 97/3 by weight mixture of an organic solvent and water and bringing the resulting dispersion into contact with activated carbon and acid clay or activated clay.